The province's Special Investigations Unit has been called in after a man died following an interaction with police.
Toronto officers were called to an area around Old Weston Road and St Clair around noon on Friday.
Witnesses reported seeing a man with a knife in each hand, who was waving them around and screaming.
The SIU says a police officer discharged a conducted energy weapon and the man went into medical distress. He was pronounced dead in hospital.
The SIU is asking anyone with information to contact the lead investigator at 1-800-787-8529.
The SIU is called in, when an 'interaction' with police, results in death or serious injury.